linux-kernel - Re: [PATCH v5 09/16] cxl/pci: Map CXL PCIe Upstream Switch Port RAS registers

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Message-ID: <73855ef4-7540-486f-9a4d-e73cfd286216@amd.com>
Date: Tue, 14 Jan 2025 16:11:12 -0600
From: "Bowman, Terry" <terry.bowman@....com>
To: Ira Weiny <ira.weiny@...el.com>, linux-cxl@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
 nifan.cxl@...il.com, dave@...olabs.net, jonathan.cameron@...wei.com,
 dave.jiang@...el.com, alison.schofield@...el.com, vishal.l.verma@...el.com,
 dan.j.williams@...el.com, bhelgaas@...gle.com, mahesh@...ux.ibm.com,
 oohall@...il.com, Benjamin.Cheatham@....com, rrichter@....com,
 nathan.fontenot@....com, Smita.KoralahalliChannabasappa@....com,
 lukas@...ner.de, ming.li@...omail.com, PradeepVineshReddy.Kodamati@....com,
 alucerop@....com
Subject: Re: [PATCH v5 09/16] cxl/pci: Map CXL PCIe Upstream Switch Port RAS
 registers




On 1/14/2025 4:02 PM, Ira Weiny wrote:
> Terry Bowman wrote:
>> Add logic to map CXL PCIe Upstream Switch Port (USP) RAS registers.
>>
>> Introduce 'struct cxl_regs' member into 'struct cxl_port' to cache a
>> pointer to the CXL Upstream Port's mapped RAS registers.
>>
>> Also, introduce cxl_uport_init_ras_reporting() to perform the USP RAS
>> register mapping. This is similar to the existing
>> cxl_dport_init_ras_reporting() but for USP devices.
>>
>> The USP may have multiple downstream endpoints. Before mapping AER
>> registers check if the registers are already mapped.
>>
>> Signed-off-by: Terry Bowman <terry.bowman@....com>
>> ---
>>  drivers/cxl/core/pci.c | 15 +++++++++++++++
>>  drivers/cxl/cxl.h      |  4 ++++
>>  drivers/cxl/mem.c      |  8 ++++++++
>>  3 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
>> index 1af2d0a14f5d..97e6a15bea88 100644
>> --- a/drivers/cxl/core/pci.c
>> +++ b/drivers/cxl/core/pci.c
>> @@ -773,6 +773,21 @@ static void cxl_disable_rch_root_ints(struct cxl_dport *dport)
>>  	writel(aer_cmd, aer_base + PCI_ERR_ROOT_COMMAND);
>>  }
>>  
>> +void cxl_uport_init_ras_reporting(struct cxl_port *port)
>> +{
>> +	/* uport may have more than 1 downstream EP. Check if already mapped. */
>> +	if (port->uport_regs.ras)
>> +		return;
>> +
>> +	port->reg_map.host = &port->dev;
>> +	if (cxl_map_component_regs(&port->reg_map, &port->uport_regs,
>> +				   BIT(CXL_CM_CAP_CAP_ID_RAS))) {
>> +		dev_err(&port->dev, "Failed to map RAS capability.\n");
>> +		return;
> Why return here?  Actually I think 8/16 had the same issue now that I see
> this.
>
> Other than that:
>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
>
> [snip]
If RAS registers fail mapping then exit to avoid CXL Port error handler initialization.
The CXL Port error handlers rely on RAS registers for logging and without mapped RAS
registers the error handlers will return immediately.

Regards,
Terry